CMS-855O: Medicare Enrollment for Eligible Ordering and Certifying Physicians and Other Eligible Professionals
Abbreviated Medicare enrollment for clinicians who order or certify items and services for Medicare beneficiaries but do not personally bill Medicare.
Primary source
CMS-855O Form — CMS.gov →https://www.cms.gov/medicare/cms-forms/cms-forms/downloads/cms-855o.pdf
Verified May 23, 2026 · This is the authoritative regulator URL. The summary below is a research aid; the linked source controls.
The CMS-855O is the abbreviated Medicare enrollment application for physicians and other eligible professionals who order or certify items or services for Medicare beneficiaries but do not bill Medicare directly. Examples: hospital-employed physicians who order DME for discharged patients, retired physicians who continue to write Medicare orders, residents and fellows who order certain items.
Medicare requires that orders, referrals, and certifications be made by an enrolled provider. Without a current enrollment, the downstream supplier or DME billing claim will be denied because the ordering NPI is not enrolled in Medicare.
The 855O is narrower than the 855I: no billing privileges, no reassignment, no practice location enrollment. It establishes the ordering NPI in PECOS so downstream claims pass the ordering/referring NPI validation edits.
Revalidation: 5-year cycle, same as the 855I.
Common scenario: a retired physician who is now an emeritus consultant continues to sign occasional orders for former patients. Without an 855O, the patients' claims for those ordered items will be denied even though the underlying service is medically necessary and the physician is licensed.
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Related regulations
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Related across the archive
- RegulationCMS-855I: Medicare Enrollment Application for Individual Physicians and Non-Physician PractitionersIndividual Medicare enrollment vehicle for physicians, NPPs, and certain other individual suppliers; required for any clinician billing Medicare under their own name.
- RegulationCMS-855R: Reassignment of Medicare BenefitsAuthorization form for an individual physician/NPP to reassign their right to collect Medicare payment to a group practice or other eligible entity.
- RegulationCMS-855S: DMEPOS Supplier EnrollmentMedicare enrollment application for durable medical equipment, prosthetics, orthotics, and supplies suppliers, with heightened standards including accreditation and surety bond.
- GlossaryCAQH CredentialingThe CAQH ProView database used by most commercial payers to credential providers.
- GlossaryCMS-855 (Medicare Enrollment Application)Family of Medicare enrollment applications: 855A (institutional), 855B (group), 855I (individual), 855O (ordering/referring), 855R (reassignment).
- GlossaryCredentialingThe process by which a payer verifies a provider's qualifications and grants participation in the network.
- GlossaryDeactivationRemoval of a provider from Medicare's enrollment file, typically for failing to revalidate, billing inactivity, or final adverse action.
- GlossaryHospital CredentialingThe process by which a hospital medical staff verifies and grants privileges to a physician.
Last reviewed May 23, 2026 · Citation verified May 23, 2026
Research aid, not legal advice. This summary is an administrative research aid prepared by D3rx. It does not certify compliance, provide legal advice, replace counsel, or guarantee an audit outcome. For authoritative regulatory text follow the primary source link at the top of this page. The practice remains responsible for reviewing, adopting, and maintaining its compliance program.